Kidney Labeling Exercise

Ureters, Bladder and Urethra The Urinary System Ureters, Bladder and Urethra

Ureters The ureters are slender tubes each 25 to 30 cm long and 6mm in diameter: The superior end of each ureter is continuous with the pelvis of the kidney The ureters are passageways that carry urine from the kidneys to the bladder

Ureters The ureters play an active role in urine transport: Smooth muscle layers in their walls contract to propel urine into the bladder by peristalsis Once urine has entered the bladder, it is prevented from flowing back into the ureters by small valve-like folds of bladder mucosa that flap over the ureter openings

Urinary Bladder The urinary bladder is a smooth, collapsible, muscular sac that stores urine temporarily If the interior of the bladder is scanned, 3 openings are seen: 2 ureter openings 1 single opening of the urethra The smooth triangular region of the bladder base outlined by these 3 openings is called the trigon

Trigone Infections tend to persist in this region In males, the prostate gland surrounds the neck of the bladder where it empties into the urethra

Bladder The bladder wall contains 3 layers of smooth muscle, collectively called detrusor muscle The mucosa of the bladder wall is a special type of epithelium called transitional epithelium Urine in bladder: When the bladder is empty, it is collapsed and its walls are thick and thrown into folds When the bladder is full, the bladder expands and rises in the abdominal cavity When the bladder is really stretched, it becomes firm and pear shaped

Urethra The urethra is a thin-walled tube that carries urine by peristalsis from the bladder to the outside of the body At the bladder-urethra junction, a thickening of the smooth muscle forms the internal urethral sphincter: an involuntary sphincter that keeps the urethra closed when urine is not being passed A second sphincter, the external urethral sphincter: it is fashioned by skeletal muscle and can be controlled voluntarily

Urethra (Female) The length and relative function of the urethra differ in the 2 sexes: In female: It is about 3-4 cm long and its external orifice (opening), lies anteriorly to the vaginal opening Its function is to conduct urine to the body exterior

Urethra (Male) In male: It is about 20 cm long and has 3 named regions: Prostatic, membranous and spongy urethra There are 2 functions: It carries urine out of the body It provides the passageway through which sperm is ejected from the body In males, the urethra is part of both the urinary and reproductive systems

Micturition Micturition or voiding, is the act of emptying the bladder The 2 sphincters control the flow of urine from the bladder: The bladder continues to collect urine until about 200 ml have accumulated Stretching of the bladder wall activates stretch receptors This cause the bladder to go into reflex contractions As the contractions become stronger, stored urine is forced past the internal sphincter. It is then that a person feels the urge to void

Micturition Because the lower external sphincter is skeletal muscle and is voluntarily controlled, we can choose to keep it closed and postpone bladder emptying temporarily After 200-300 ml more have been collected, the micturition reflex occurs again. Eventually, micturition occurs whether one wills it or not

Incontinence Incontinence occurs when we are unable to voluntarily control the external sphincter: Incontinence is normal in children 2 years old or younger, because they have not yet gained control over their voluntary sphincter After the toddler years, incontinence is usually a result of emotional problems, pressure (pregnancy) or nervous system problems (stroke or spinal cord injury)

Urinary Retention Urinary retention is essentially the opposite of incontinence It is a condition in which the bladder is unable to expel its contained urine Causes: After surgery in which general anesthesia has been given Enlargement of the prostate gland